There are a large number of devices for delivering medication orally for absorption in the respiratory system and one strong trend is to develop inhalation devices for self-administration. Traditionally oral medication was intended for treatment of diseases in the trachea, bronchi and/or lungs, and in particular Acute or chronic symptoms of asthma. However, much research is now performed on administration of medicament via the lungs of other ailments due to beneficial absorption rate and reduced side effects. Further, pulmonary administration provides a greater safety than delivery devices using needles because of the problem with possible contamination from a used needle.
However, there are a number of medicament compositions that are not compatible with existing devices and there are further a number of drawbacks with existing devices. For example aerosol dispensers utilise a propellant which provides the force to aerosolize the medicament in liquid form. However, this requires a special type of pressurised canister containing liquid propellant which affects the environment. Also the ballistic aerosol has a very high speed which gives a large mouth and throat deposition giving more side effects.
Many of the devices on the market are also not very precise or reliable regarding repeated, equal dose quantities delivered. Another difficulty with some devices and/or medicament compositions is requirements regarding droplet size, drooling and also coordination between inhalation and dose delivery.
One example of a device which could be used for metered oral administration is described in the document WO 06/130100. The disclosed device comprises a plunger rod, which, when driven by a pre-tensioned helical spring, forces a stopper into a cartridge containing medicament, whereby a dose of medicament is delivered from an administration member. The administration member could be a mouth or nasal piece. While the device offers a reliable and precise dosing mechanism, there is no teaching regarding how to configure the medicament administrating member or how adjustments could be made for a variety of medicaments having different physical properties.
There are also numerous devices for delivering medicament on the market and also patented where the medicament is arranged in a generally tubular compartment having a stopper in one end of the compartment and a delivery member attached to the opposite end of the compartment, such as e.g. a needle, a medicament droplet generator or the like member capable of delivering medicament to a patient.
In order to deliver a quantity of medicament, the stopper is exposed to pressure, i.e. pushed into the compartment by a plunger rod, which could be done manually by a finger, which is the case for simple handheld syringes, or by pressure means such as springs, which is common in automatic or semi-automatic injectors.
In many instances it is desirable to be able to deliver a certain specified quantity of the medicament. This is for example the case with a multi-dose injection device, which is capable of delivering a number of specified, set, doses until the compartment is empty. One example is disclosed in the European patent application No. 05104734.8 where specific doses can be set before injection. The injection device disclosed is arranged with spring means for exerting a pressure on the medicament for delivering a specific dose, i.e. pushing the plunger rod and thus the stopper into the container.
The delivery of a dose requires a certain force from the spring means in order to overcome the friction between the somewhat resilient stopper and the inner surface of the cartridge and also to be able to press the medicament in liquid form through a rather small passage in the delivery member, possibly within a predetermined time.
Due to the elasticity of the components under pressure such as the stopper, air or gas, and also the medicament if non-newtonian, there is a prevailing pressure even when the stopper has been moved a predetermined distance and the dose has been delivered. This is in particular pronounced when handling medicament with rather high viscosity, medicament having resilient properties, and with high working pressures.
With this type of substance with high viscosity, and because very small passages of the delivery member often are used, a rather large force is required and because of the elasticity of the components, often a certain small quantity of the substance comes out of the delivery member even after performed delivery when the pressure is relieved, i.e. there is some drooling from the delivery member causing a waste of medicament and thereby decreasing the dose accuracy.
One solution is disclosed in WO 2008/020023 A1. Here a device is described for repeated dosing of small quantities of medicament. The device is particularly suitable for viscous liquids because it comprises a feature which releases pressure on the medicament inside the medicament container after delivery of a dose. This reduces the risk of dripping or drooling from the device after dose delivery.
There is thus still a need for accurate devices which facilitate oral administration of medicaments in liquid form for respiratory absorption which can be used with a variety of medicament compositions, where preferably the primary package, i.e. the medicament container, constitutes a standard and/or standard size container or syringe.